#lang play

Variations on #lang plai (the language that accompanies PLAI).

We create #lang plai in the Pleiad lab to teach Programming Languages (with PLAI and OOPLAI), but it can obviously be used for general Racket programming.

What's in there?

From #lang plai, we keep the testing support:

• test
• test/exn
• print-only-errors

We introduce several new forms:

• deftype to define structures with a concise syntax that directly corresponds to the constructor syntax

(deftype Expr
  (num n)
  (add l r))

• def to define identifiers, possibly using pattern matching

(def x 10)
(def (cons a b) (get-some-cons)) ;; pattern matching, defines a and b at once

• defun as an alias for define (for the convenient function definition syntax)

(defun (interp expr)
  ....)

• defmac as an extended version of define-syntax-rule, which supports keywords and captures

(defmac (for from low to high in bodies ...)
  #:keywords from to in
  #:captures it
  ....)

How does it look in practice?

For observing def, defun and deftype in action, see various interpreters from PLAI rewritten in #lang play.

For uses of defmac, see OOPLAI, an OOP-with-macros supplement to PLAI.

Installation

In DrRacket (v5.3.6 or newer) go to File > Install Package > play